Best Plants Under Big Trees
Use at least a 3-inch layer of mulch to conserve soil moisture around new plantings, says Matt Fox, horticulture manager at the Iowa Arboretum (30 miles northwest of Des Moines near Madrid).
Keep mulch an inch away from tree trunks so it won't smother the tree roots or introduce pests or disease. Any new plantings should go at least 1 foot inside a tree's drip line.
Dry-shade-tolerant plants need extra water their first summer and fall, but then should survive with little added moisture except in extreme drought.
An easy, common plant for dry shade is Vinca minor (left). It spreads quickly and looks attractive, with glossy leaves and purple-blue flowers.
Other interesting possibilities for dry shade include hostas, Canadian wild ginger, fringed bleeding-hearts, 'Pink Skyrocket' foamflower and 'PJM' rhododendron (details on next slides).